Full-wave rectifier



J1me 1951 B. P. DE LANY ET AL 2,555,843

FULL WAVE RECTIFIER Filed Aug. 4, 1949 1720672 fans .fieatre'cez arsafiflelany @362 l. CbpeZand .iZ/arneys Patented June 5, 1951 FULL-WAVE RECTIFIER Beatrice Pearson De Lany, Miami Beach, Fla., and Paul L. Copeland, Chicago, Ill.

Application August 4, 1949, Serial No. 108,544

7 Claims. 1

This invention relates to a full-wave rectifier which has for one object to provide a cold cathode rectifier suitable for use in communications, control devices and vapor discharge tubes used in lighting,

Another object is to provide a cold cathode full-wave rectifier in which arcs are readily initiated.

Another object is to provide a rectifier of the type indicated, including a constriction to facilitate the transition from glow to arc.

Other objects will appear from time to time in the specification and claims.

The invention is illustrated more or less diagrammatically in the accompanying drawing, wherein:

Figure l is a section through one form of rectifier tube;

Figure 2 is a diagram illustrating the rectifier tube in a conventional full-wave rectifier circuit;

Figure 3 is a fragmentary section of the tube showing a modified form of the anode.

Like parts are indicated by like characters in the specification and drawing.

As shown in the drawing, I is an envelope or tube from which the air has been exhausted. It is formed of insulating material and may conveniently be formed of glass or analogou material. Although it may not be transparent, it will frequently be formed of transparent glass. As shown, the tube I is provided with a reduced or constricted portion 2 so that the shoulder 3, where the portion 2 joins the main tube or envelope I, may be considered a restriction of the envelope I.

Two metal anodes 4 and 5 are positioned within the envelope I. Each of the anodes has connected to it a conductor or wire 6 and 1, respectively, which pass outwardly through the wall of the tube I and are sealed as at 8 and 9, respectively. Air is exhausted from the tube through an opening subsequently sealed. Such a seal is indicated diagrammatically at I0.

An inert gas may, if desired, be introduced into the tube after the air is removed, and the inert gas, if present, may be at a pressure of 1-2 mm. This may be helium.

There is contained in the constricted portion 2 a metal pool cathode ll. This pool may be formed of mercury or equivalent material which will remain liquid at normal operating temperatures. A wire or conductor 12 passes through the wall of the restricted portion 2 and into the oathode pool, as shown. It is sealed in the envelope as at I3. A quantity of magnesium oxide powder I4 is placed upon and supported by the upper surface of the cathode pool I I. Magnesium oxide powder is a suitable material for the purpose, but the invention is not limited to the use of this material. Other insulating or semi-conducting material may be substituted for the magnesium oxide.

Asshown in Figure 2, the tube of the present invention is inserted in a more or less conventional full-wave rectifier circuit. This circuit includes a transformer comprising a primary coil it, a secondary coil I 6 and a metallic core II positioned between the two. Current is supplied to the primary coil I5 through wires or conductors l3 and 49. One end of the secondary coil I6 is connected to the member 6, and hence to the anode and the other member of the secondary coil I5 is connected to the member I, and hence to the anode 5.

A filter 2%} comprises coils 2| and 22. The coil 25 is connected to the cathode by means of the member ill. The filter is connected by a conductor 23 to the load indicated diagrammatically at 24 and the opposite end of the load 24 is connected by a conductor 25 to the secondary coil IS.

A condenser 26 is connected to the filter 26 by a conductor 21 and is also connected to the conductor 25 by a conductor 28. A second condenser 2?) is connected to the conductor 23 by a conductor 35 and to the conductor 25 by a conductor 3| The load 24 is indicated only diagrammatically and the showing is merely to indicate that a load of any nature is inserted at the point indicated between the members or conductors 23 and 25.

The cold cathode rectifier of this invention is intended as a substitute for the currently used hot cathode rectifiers. Such hot cathode rectifiers have limited life because of the sputtering of the active material of the cathode. This sputtering is serious enough when such tubes are operated within their designed ratings. It becomes disastrous if these ratings are exceeded and the usefulness of the tube may thereby be destroyed in a period of overload. For these and other reasons, pool type rectifiers, as heretofore known, have proven most suitable for the rectification of large currents. One of the problems occurring in the design of a cold cathode tube or rectifier is to provide a construction in which a satisfactory glow within the tube is established. In the past it has proven difficult to provide a construction in which the transition from the glow to a suitable working arc occurs rapidly. The constriction formed by the shoulder 3 in the present invention not only stabilizes the arc formed but facilitates the glow to are transition, and thus causes rapid arc formation and hence produces a construction suitable for practical use.

The constriction by itself is not necessarily effective in accomplishing arc initiation. The presence of an insulator or a semi-conductor on the cathode facilitates the glow to are transition. Thus, the presence in the present construction of the constriction and the presence of the insulator or semi-conductor, such as the magnesium oxide, upon the surface of the cathode pool results in a tube which is easily started as an are because the glow to arc transition occurs promptly. Such a tube produces not only quick starting, but also produces long-lived and stable arcs at low currents, low voltages andv low ambient temperatures, and such a tube, in practice, starts promptly and operates Well as a full-wave rectifier.

The lead-in wires'or conductors 6 and I may be provided with insulation 32, as shown in Fig- .ure 1.

In.the modified form of Figure 3, the anodes are shaped to conformgenerally to a portion of the tube and are placed very close to the inner surface of the tube. A clearancebetween the inner face of the .tube l and the anode 33 of the order. of -1 mm. is preferred. In this form, insulation (i i-is provided on the lead-in wires. small clearance between the anodes, as shown in Figure 3, and the inner surface of the envelope is such. that the envelope itself acts as an insulating. coating or the insulating member of the anodes. of either or both of the anodes is covered with an insulatingmaterial to shieldit from the discharge. The anodes will, ordinarily, be formed of sheet metal and the backs may be covered with insulating material. of thefronts of the anodes 4 and 5 may be covered with insulating. material, thus, limiting the area of the anodes which is, exposed to the discharge. In the modified form of Figure 3, the insulating The If desired, also, parts In the form of Figure l, a portion coating. is omitted. from the back because, as

stated above, the envelope I, itself, acts as the insulating coating or member for the anodes 33. Ifdesired, a portion of the exposed face of the anodesmay. also be covered with insulatingvmaterial.

The presenceof the metal anodes in either form partially covered with insulating material, or insulated by the envelope, provides for heat radiation from the covered portion, but in view of the insulating coating or the insulating effect of the envelope in the modified-form, there -isno electrical conductivity in the covered portions of the anode or in the portion of the anode 33 facing the envelope 1. The spacing of the anodes 33 from the envelope I has been referred to as being of the order of 1 mm. Whatever the exact dimension of the space between the ancdesand the envelope, the anode is placed within a distance from the inner surface of the envelope which is not greater than the cathode'dark space.

Although we have shown an operative form of our invention, it will be recognized that many changes in the form, shape and arrangement of parts can be made without departing from the spirit of the invention, and our showing is, therefore, to be taken as, in a sense, diagrammatic.

The use and operation of this invention are as follows:

With a rectifier tube, as shownin detail. in Figure 1, associated in a rectifier circuit such,

4 for example, as that shown in Figure 2, the assembly when connected to a source of alternating current is ready for operation when voltage is applied to the transformer and glow is initially established between the anodes. This current does not flow through the load and the cathode is at the potential of the center tap of the transformer. The cathode fall in the glow between the anodes causes the space surrounding the cathode to be positive with respect to the cathode. Under these conditions, ositive ions from the discharge between the anodes are driven toward the cathode. These positive ions charge the semi-conducting particles and make them sufliciently positive to cause the formation of an arc with a cathode spot on the mercury surface. The cathode spot then supplies an electron current to whichever anode is positive, and the device thus works as a full-wave rectifier of high efiiciency.

From this description of the operation it is clear thatno heating current is required for the cathode, and cathodes of the type shown, when arranged in the manner indicated, will supply very large currents without deterioration. The powder M, which is positioned on the cathode pool H, whatever its exact nature, is chosen from a material which is a pure electrical conductor. When the device of the invention is in use, the powder it becomes electrostatically charged and produces an intense electrostatic field, thus facilitating the establishment of a cathode spot.

We claim:

1; In combination, an air-tight envelope formed of insulating material and substantially freefrom air, said envelope shaped to provide a depression, a pool of metal in said depression, which metal is inliquid form at operating temperature, said pool comprising a cathode and a plurality ofanodes positioned within said envelope spaced away from said cathode, electrical-connections to said anodes and to said cathode, and a quantity of magnesium oxide upon the upper surface of said cathode pool, said depression comprising means for concentrating the action of the anodes upon said pool.

2. In combination, an air-tight envelope formed of insulating material and substantially free from air, a quantity of inert gas at relatively low pressure. contained within said envelope, said envelope shaped to provide a depression, a pool, of metal in said depression, which metal is in liquidform at operating temperature, said pool comprising a cathode and a plurality of anodes openly positioned within said envelope spaced away from said cathode, electrical connections to said anodes and to said cathode, and a quantity of magnesium oxide upon the upper surface of said cathode pool, said depression comprising means for concentrating the action of the anodes upon said pool.

3. In combination, an air-tight envelope formed of insulating material and substantially free from air, a quantity of inert gas at relatively low pressure contained within said envelope, said envelope shaped to provide a depression. of restricted diameter with respect to the diameter of said envelope as a whole, there being a shoulder about the upper end of said restriction, a pool of metal in said depression and below said shoulder, which metal is in liquid form at operating temperature, said pool comprising a cathode and a plurality of anodes positioned within said envelope spaced away from said cathode, electrical connections to said anodes and to said cathode, and a quantity of magnesium oxide upon the upper surface of said cathode pool, the restriction of said depression comprising; means for concentrating the action of the anodes upon said pool.

4. In combination, an air-tight envelope formed of insulating material and substantially free from air, said envelope shaped to provide a depression, a pool of metal in said depression, which metal is in liquid form at operating temperature, said pool comprising a cathode and a plurality of anodes positioned within said envelope spaced away from said cathode, electrical connections to said anodes and to said cathode, and a quantity of semi-conducting material upon the upper surface of said cathode pool, said depression comprising means for concentrating the actionof the anodes upon said pool.

5. In combination, an air-tight envelope formed of insulating material and substantially free from air, a quantity of inert gas at relatively low pressure contained Within said envelope, said envelope shaped to provide a depression, a pool of metal in said depression, which metal is in liquid form at operating temperature, said pool comprising a cathode and a plurality of anodes positioned within saidenvelope spaced away from said cathode and insulation placed upon a portion of the surface of said anodes, electrical connections to said anodes and to said cathode, and a quantity of semi-conducting material upon the upper surface of said cathode pool, said depression comprising means for concentrating the action of the anodes upon said pool.

6. In combination, an air-tight envelope formed of insulating material and substantially free from air, a quantity of inert gas at relatively low pressure contained within said envelope, said envelope shaped to provide a depression of restricted diameter with respect to the diameter of said envelope as a whole, a pool of metal in said depression, which metal is in liquid form at operating temperature, said pool comprising a cathode and a plurality of anodes positioned within said envelope spaced away from said cathode, electrical connections to said anodes and to said cathode, and a quantity of semi-conducting material upon the upper surface of said cathode pool, the restriction of said depression comprising means for concentrating the action of the anodes upon said pool.

7. In combination, an air-tight envelope formed of insulating material and substantially free from air, a quantity of helium at relatively low pressure contained within said envelope, said envelope shaped to provide a depression of restricted diameter with respect to the diameter of said envelope as a whole, a pool of metal in said depression, which metal is in liquid form at operating temperature, said pool comprising a cathode and a plurality of anodes positioned within said envelope spaced away from said cathode, electrical connections to said anodes and to said cathode, and a quantity of semiconducting material upon the upper surface of said cathode pool, the restriction of said depression comprising means for concentrating the action of the anodes upon said pool.

BEATRICE PEARSON DE LANY. PAUL L. COPELAND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 21,088 Robinson May 16, 1939 1,156,227 Hewitt Oct. 12, 1915 1,178,542 Thomas Apr. 11, 1916 1,696,880 Donle Dec. 25, 1928 1,741,017 Feild Dec. 24, 1929 1,859,875 Kern May 24, 1932 1,943,845 Spaeth Jan. 16, 1934 

